new helper to run chroot prep scripts in bulk
the primary change here is to introduce a helper for running chroot prep scripts in bulk
this (1) tidies things up a bit, (2) is helpful when executing individual scripts such as sometimes may be done during development
there's also a fix on top for adding use of chroot_tmpfs in the binary stage and one for removing unnecessary execution of lb chroot_debianchroot remove
there
Edited by Lyndon Brown